1. Field of the Invention
The present invention relates to an apparatus for testing a liquid crystal display panel, and particularly, to an apparatus for testing a liquid crystal display panel which is capable of easily fixing a polarizer having a large size by inserting the polarizer into a rotatable polarizer fixing unit.
2. Discussion of the Related Art
With the continuing deployment of various portable electric devices such as mobile phones, personal digital assistants (PDA), notebook computers, various types of flat panel display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum florescent displays (VFDs), having a compact construction, light weight, and low power-consumption characteristics are being developed. LCDs are extensively used because they are drivable with relatively simple circuitry and because of their superior ability to display images.
The liquid crystal display (LCD) device takes advantage of the refractive index anisotropy of liquid crystal to display information on a screen. As shown in FIG. 1, a typical LCD device 1 includes a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 disposed between the lower substrate 5 and the upper substrate 3. The lower substrate 5 is a switching device array substrate. Although not shown, the lower substrate 5 is provided with a plurality of pixels, each of which is provided with a switching device such as a Thin Film Transistor (TFT). The upper substrate 3 is a color filter substrate and includes a color filter layer for implementing a substantial color. In addition, the lower substrate 5 and the upper substrate 3 are respectively provided with a pixel electrode and a common electrode and are each coated with an alignment layer for aligning liquid crystal molecules of the liquid crystal layer 7.
The lower and upper substrates 5 and 3 are bonded to each other by a sealant 9. The liquid crystal layer 7 is formed between the lower and upper substrates 5 and 3. A driving device applies potentials to the pixel and common electrodes to control using the switching device formed at the lower substrate 5 to control the orientation of the liquid crystal molecules and accordingly to control an amount of light transmitted through the liquid crystal layer 7 to display images.
A fabrication process of the LCD device includes a switching device array substrate forming process for forming the switching devices at the lower substrate 5, a color filter forming process for forming the color filter at the upper substrate 3, and a cell forming process. The fabricating process of the LCD device will now be explained with reference to FIG. 2.
First, as part of the switching device array forming process, a plurality of gate lines and a plurality of data lines are arranged on the lower substrate 5 to define pixel regions. A TFT to be used as a switching device is connected to each gate line and each data line and is formed in each pixel region (S101). The switching device array forming process further includes forming a pixel electrode connected to the TFT to drive the liquid crystal layer 7 when a signal is applied via the TFT.
The color filter forming process include forming a color filter layer for implementing R, G and B colors on the upper substrate 3, and a forming common electrode thereon (S104).
An alignment layer is coated on each of the upper and lower substrate 3 and 5. The alignment layers are rubbed to provide an alignment controlling force or a surface fixing force to set the initial alignment (i.e., a pretilt angle and an alignment direction) of the liquid crystal molecules of the liquid crystal layer 7 disposed between the upper and lower substrates 3 and 5 (S102 and S105). Spacers are dispersed over the lower substrate 5 for maintaining a cell gap between the upper and lower substrates 3 and 5 and a sealant 9 is disposed on an outer periphery of the upper substrate 3 for bonding together the lower substrate 5 and the upper substrate by applying a pressure thereto (S103, S106 and S107).
The lower and upper substrates 5 and 3 are formed from large sized glass substrates. In other words, a plurality of panel regions are formed on the large glass substrates and the TFT (i.e., the switching device) and the color filter layer are formed on each panel region. Accordingly, the glass substrate must be cut and processed in order to fabricate unit LCD panels (S108). A liquid crystal may be injected into the processed unit LCD panels through a liquid crystal injection opening and then the injection opening is encapsulated to form the liquid crystal layer 7. Each unit LCD panel is inspected to complete the fabrication process of the LCD panel (S109 and S110).
The LCD panel is typically tested (inspected) by a visual inspection and an electrical lighting test. The lighting test is performed by applying a signal to a completely fabricated LCD panel to detect (test) whether various electric devices are operating normally, while the visual inspection is performed by an operator conducting a naked eye inspection of the LCD panel to determine whether the LCD panel has been defectively fabricated.
A typical apparatus for visually inspecting an LCD panel includes a test board having a lamp therein for outputting light. An LCD panel is transferred to the visual inspection apparatus to be placed on the test board and a polarizer is positioned on the LCD panel. A signal is applied to the LCD panel and the LCD panel is illuminated by light transmitted from the lamp provided in the test board. The operator observes light transmitted through the LCD panel to detect defects in the LCD panel.
FIGS. 3A and 3B show a related art visual inspection apparatus for testing an LCD panel appearance, wherein FIG. 3A is a side sectional view of the visual inspection apparatus and FIG. 3B is a plane view thereof.
As shown in FIGS. 3A and 3B, a related art apparatus for visually inspecting an LCD panel 20 includes a test board 22 including a lamp installed therein for transmitting light to the LCD panel 1 placed thereon; a camera 24 positioned at an upper portion of the test board 22 for capturing alignment marks (not shown) formed at an outer periphery of the LCD panel 1 to thus determine whether the LCD panel 1 has been aligned on the test board 22; a jig 32 disposed at a lower portion of the test board 22 supporting a polarizer 30 and having holes 27; and a plurality of jig pins 26 formed at the test board 22 to be inserted into the holes 27 of the jig 32 to thus fix the jig 32 to the test board 22, thereby fixing the polarizer 30 onto the LCD panel 1.
The test board 22 is inclined by about 60° relative to the ground and has a lamp therein. When an operator puts the LCD panel 1 on the test board 22, the camera 24 captures the alignment marks formed on the LCD panel 1 to provide information regarding the state of alignment of the LCD panel 1. With the LCD panel 1 aligned on the test board 22, the operator inserts the jig pins 26 formed at the test board 22 into the holes 27 formed in the jig 32 to position the polarizer 30 on the LCD panel 1. With the polarizer fixed, a signal is applied to the LCD panel 1 and a transmissivity of light transmitted through the LCD panel is changed according to a signal applied to the LCD panel 1. The operator observes the light transmitted through the polarizer 30 to evaluate the quality of the LCD panel.
The jig 32 supports the polarizer 30. The operator manipulates the jig 32 rather than the polarizer 30 to position the polarizer 30 on the test board 22. The jig pins 26 are inserted into the holes 27 formed in the jig 32 to fix the jig 32, and thus the polarizer 30, onto the test board 22.
However, the above described visual inspection apparatus for the LCD panel may generate problems as follows.
In order to fix the polarizer 30 by inserting the jig 32 into the jig pins 26, the operator must manually hold the jig 32 while inserting the jig pins 26 of the test board 22 into the holes 27 of the jig 32. However, with a the large-sized LCD panel 1, the corresponding large size of the polarizer 30 makes it physically difficult or impossible for the operator to manually insert the jig pins 26 into the holes 27 of the jig 32. In addition, while attaching or detaching the polarizer 30, the polarizer 30 may strike the camera 24, resulting in damage to the camera 24 or to the polarizer 30.